Thread breaks detector having transparent thread guide



June 24, 1969 MELKQNJAN ETAL 3,452,209

' THREAD BREAKS DETECTOR HAVING TRANSPARENT THREAD GUIDE Filed Dec. 19, 1966 U.S. Cl. 250-219 10 Claims ABSTRACT OF THE DISCLOSURE A thread breakage detector in which the thread passes over a member having an opaque guide surface provided with a light-transmitting portion of such size as to be normally covered by the thread. Light is directed at this portion from one side of the member and a photocell is provided on the other side of the member and located in the path of the light. The light can pass through the surface portion to the photocell only if the thread breaks and thereby uncovers the surface portion.

Background of the invention This invention relates to a thread breakage detector in general, and to a photoelectric thread breakage detector in particular, wherein breakage of the thread actuates a photosensitive cell which in turn controls other monitoring devices.

Known photoelectric thread breakage detectors comprise a source of light, a photosensitive cell influenced thereby, and a guide for the thread arranged therebetween. In known detectors the thread guides have threadaccommodating apertures which are of circular or polygonal cross-section and which must berelatively large since, when the thread breaks, thread end must be threaded through such apertures to be returned to that part of the thread processing arrangement at which it can be rejoined with the forward end of the thread portion left behind. This obviously requires these apertures to be large enough to permit resonably easy threading of the end of the broken thread therethrough. On the other hand, however, the required size of these apertures permits excessive radial play of the thread during advancement of the same, in consequence of which the passage of light from the light source to the photosensitive cell is intermittently permitted and interrupted as the thread moves radially in the aperture. This results in actuation of the photocell even when the thread is not broken. Attempts have been made to use weak light sources so that the quantity of light which passes through the aperture when the same is only partially uncovered during radial play of the thread, is not suificient to activate the photocell. However in these cases it is then necessary to provide expensive amplification devices in connection with the photoelectric cell.

Summary of the invention It is therefore a general purpose of the invention to overcome the disadvantages outlined above with respect to the prior art.

In accordance with one feature of the invention we provide a thread guide means having a guide surface over which a thread is adapted to pass, said surface having a light transmitting surface portion adapted to be covered by said thread during passage thereof over said United States Patent 3,452,209 Patented June 24, 1969 surface, all portions of said thread guide means other than said light transmitting surface portion thereof being opaque.

Such an arrangement requires minimum amplification equipment and is therefore inexpensive to construct.

Furthermore, a detector of the type described considerably simplifies threading of the broken thread ends and thus permits the apertures for the thread to be made much smaller than heretofore possible.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

Brief description of the invention FIG. 1 shows a photoelectric thread breakage detector according to the invention in a somewhat schematic perspective view;

FIG. 2 is a sectional view taken on the line II-II of FIG, 1;

FIG. 3 is a view of the thread guide member used in the embodiment of FIGS. 1 and 2, as seen from the right in FIG. 2;

PI. 4 is a sectional view taken on the line IV-IV of FIG. 3;

FIG. 5 is a view of the thread guide member in FIG. 3, but as seen from the left in FIG. 2;

FIG. 6 is a top plan view of FIG. 5;

FIG. 7 is a sectional view through another thread guide means for use in the arrangement of FIGS. 1 and 2; and

FIG. 8 is a sectional view taken on the line VIIIVIII of FIG. 7.

Description of the preferred embodiments Discussing now the drawings in detail, and firstly FIG. 1 thereof, it will be seen that the novel thread break detector comprises a housing 1 within which there is located a thread guide means 5. Reference numeral 3 designates part of a light source as will be more fully discussed with respect to FIG. 2.

FIG. 2 is a section taken on the line II-II of FIG. 1 and shows the novel detector in more detail. It will be noted that the housing 1 accommodates a light source, such as the light bulb 2 which is held by the socket 3 carried by the housing. The bulb 2 is arranged at one end of the housing 1 and adjacent the other end thereof there is arranged a light-sensitive sensor, such as a photocell 4. Arranged intermediate the bulb 2 and the photocell 4 is a thread guide means in form of a member 5 which is provided with a thread guiding surface 8. In the illustrated embodiment it is assumed that the member 5 is a glass prism or otherwise configurated glass member provided with a groove 7, generally of V-shaped cross section. The groove 7 extends in the direction of movement of a thread 6 which is to pass through the novel detector and communicates with an inlet opening 12 and an outlet opening 11 provided in the housing 1. It is evident from FIG. 2 that the housing 1 comprises a removable cover 10 and that in the illustrated embodiment the outlet opening 11 is formed in this cover 10.

To assure that the thread 6 is constantly and reliably in contact with the guide surface 8 the latter is arcuately curved in the direction from the inlet opening 12 to the outlet opening 11. In the illustrated embodiment the guide surface 8 is assumed to constitute the bottom wall of the V-shaped groove 7 and in accordance with the invention the entire member 5, which of course is normally lighttransmitting, is metal plated to make it opaque. Excepted from such metal plating is the bottom wall of the groove 7, that is the guide surface 8 or, to be more specific, a portion of the guide surface 8. The width of this portion, which latter will thus be understood to be translucent, corresponds at most to the cross section of the thread 6 so that in normal operation of the device, that is when the thread 6 passes through the detector, the light-transmitting portion of the surface 8 will be covered by the thread. Thus, no light from the bulb 2 can pass to the photocell 4 unless the thread 6 breaks, in which case the light-transmitting portion of the guide surface -8- obviously is uncovered, permitting passage of light to the photocell 4 for activation of the same.

FIGS. 36 are various different views of the thread guide member used in the embodiment of FIG. 2. These views are believed to be largely self-explanatory. However, it should be noted that one possible modification is incorporated in FIG. 3, where it is shown that the longitudinal extension of the light-transmitting portion of the surface 8 need not be coincident with the length of this surface as seen in the direction of thread movement. This is indicated with reference numeral 9 where the lighttransmitting portion will be seen to be considerably shorter than the longitudinal extension of the surface '8.

Although it has been stated above that the member 5 is made, in the embodiment of FIGS. 1-6, from glass or a similar light-transmitting material which is subsequently suitably opaqued, it will be understood that other materials are also suitable. FIGS. 7 and 8 show such a member 5 to be made of metal. Evidently, in this case a substitute arrangement must be provided for the non-metallized light-transmitting portion of the guide surface 8 as outlined above with respect to FIGS. 1-6. In FIGS. 7 and 8 this is done by providing an aperture 13 which extends from the guide surface 8 through the remainder of the member 5 and which, evidently, must be aligned with the light source and the photocell 4. In FIGS. 7 and 8 the configuration of the guide surface is again assumed to be in the form of a V-shaped groove 7, and it is evident, particularly from FIG. 8, that the aperture 13 is provided in the bottom wall of this groove. Of course, the maximum width of the aperture 13, which can be simply a perforation or a slot extending in the direction of movement of the thread 6, will be so selected that the thread 6 covers the aperture under normal operating conditions, that is as long as no breakage has occurred.

If a material other than glass is used for making the thread guide member 5, it is important that its hardness should at least approximate that of glass since evidently the surface 8 is subjected to wear by the passage of the thread 6 thereover.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of detectors differing from the types described above.

While the invention has been illustrated and described as embodied in a thread breakage detector, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a photoelectric thread breakage detector for detector for detecting breakage of an advancing thread, in combination, a source of light; photoelectric means located in the path of light emitted by said source; and thread guide means in said path of light between said source and said photoelectric means, said thread guide means having a thread-guiding surface arranged to contact the advancing thread for guiding the same in predetermined direction and being provided with a light-transmitting portion normally covered by said thread during advancement thereof in said direction and in contact with said surface, substantially all other portions of said thread guide means which are located in the path of said light being opaque so that light from said source can impinge upon said photoelectric means only in response to uncovering of said light transmitting portion by said thread.

2. A thread breakage detector as defined in claim 1, wherein said thread guide means comprises a guide member of light-transmitting material having said guiding surface thereon, and further comprising a layer of metal plating provided at least on said guiding surface but leaving said light-transmitting portion exposed.

3. A thread breakage detector as defined in claim 1, wherein said thread guiding surface is a groove provided in said member and having a substantially V-shaped crosssection, and wherein said light-transmitting portion is provided on the bottom wall of said groove.

4. A thread breakage detector as defined in claim 1, wherein said thread-guiding surface is convexly curved as seen in the direction of advancement of said thread so as to assure constant contact of the thread with said guiding surface.

5. A thread breakage detector as claimed in claim 1, further comprising a housing with a separable cover surrounding said guide means a'nd being provided with an inlet and an outlet for said thread.

6. A thread breakage detector as defined in claim 1, wherein said thread guide means provided with said thread-guiding surface is of opaque material, and wherein said thread-guiding surface is provided with an aperture constituting said light-transmitting portion and being aligned with said source of light and with said photoelectric means.

7. A thread breakage detector as defined in claim 6, wherein said material is a metallic material.

8. A thread breakage detector as defined in claim 6, wherein the width of said aperture corresponds to the maximum diameter of the thread so that the aperture is normally covered by the thread, preventing passage of light.

9. Thread guide means having a thread contacting guide surface over which a thread is adapted to pass, said surface having a light-transmitting surface portion adapted to be covered by said thread during passage thereof over said surface, all portions of said thread guide means other than said light-transmitting surface portion thereof being opaque.

10. Thread guide means as defined in claim 9, including a thread-guiding groove having said light-transmitting surface portion at the bottom wall thereof.

References Cited UNITED STATES PATENTS 3,043,991 7/1962 Chneider et al. 3,142,832 7/1964 Horne.

RALPH G. NILSON, Primary Examiner.

M. ABRAMSON, Assistant Examiner.

US. Cl. X.R. 250222, 238 

